1. Technical Field of the Invention
The present invention relates to a process for treating keratin fibers which comprises the application to the keratin fibers, in particular human hair, of a composition comprising at least one protective agent with a log P of less than or equal to 6, followed by the application to the fibers of a heating iron or element at a temperature of greater than or equal to 60° C.
The present invention also relates to the use of the said process for protecting keratin fibers, in particular human hair, against the effects of UV radiation and more especially for protecting artificially dyed hair.
2. Description of Background and/or Related and/or Prior Art
It is well known that the hair is sensitized or embrittled to varying degrees by the action of atmospheric agents and especially the light. Many publications disclose that natural light destroys certain amino acids of the hair. These attacking factors impair the hair fiber and reduce its mechanical properties, for instance the tensile strength, the breaking load and the elasticity, or its resistance to swelling in an aqueous medium. The hair is then dull, coarse and brittle.
It is also known that light especially has a tendency to attack the natural color of the hair, and also the artificial color of dyed hair. The color of the hair gradually fades or turns to relatively unattractive or undesirable shades.
The effect of light is even more visible on hair dyed by artificial coloration, in particular oxidation dyeing or direct dyeing. In this case, exposure to light leads to degradation of the dyes present both in the hair and on its surface. This results in substantial fading and/or changing of the color of the hair.
Substances for protecting the hair against the degradation caused by atmospheric attacking factors, such as light, have been sought for many years in the cosmetics industry. Products that protect the integrity of keratin fibers, i.e., their composition, their surface condition, their natural or artificial color and their intrinsic mechanical properties (the tensile strength, breaking load and elasticity, or their resistance to swelling in an aqueous medium) are sought in particular.
To combat these types of degradation of hair keratin, it has already been proposed to use protecting agents such as organic UV-screening agents, antioxidants, chelating agents or free-radical scavengers.
Certain substances capable of screening out light radiation, for instance 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid or salts thereof (FR-A-2,627,085), 4-(2-oxo-3-bornylidenemethyl)benzenesulfonic acid or salts thereof (EP-A-329,032) or lactoferrin (FR-A-2,673,839) have thus been proposed.
JP 05-043437 discloses dye compositions containing 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid or salts thereof, an aromatic alcohol and an acidic direct dye.
However, the current cosmetic compositions containing protecting agents are not entirely satisfactory, in particular on hair dyed with blue oxidation dyes, for instance those obtained with couplings comprising meta-phenylenediamines.